Alloy articles for use at high temperatures



Patented July '4, 1950 UNITE Df ES rarest AEILOYARDIGEES FOR-USE AT HIGH TEMPERATURES Russell Franks and William. 0.- Binder, Niagara. Falls, N," Y2, assi'gnors, by mesne assignments, to Union Garb'ideand. Carbon Corporation, a

corporation ot New York I v No Drawing. Application; 9,1946, .SeriallNo. 668,329

3iClaims.

This invention relates to alloy-articlesd'esigned particularly for use in applications where great strength at very high temperatures is'required;

The continued development of such devices as superchargers, gas turbines, jet propulsion apparatus and the like depends upon the production of workable metals and alloys that are strong at the high temperatures at which such devices operate. Although several alloys have been proposed for'use in high temperature applications, the utility of such alloys has been limited either because they are'not hot-workable or machinable or because they become brittle upon continued exposure to elevated temperatures. One characteristic of highly. alloyed ferrous metals which complicates the problem considerably is that as the ferrous solid solution is more heavily loaded with alloying materials to increase the hi h-temperature strength; the high-temperature stability tends to decrease so that upon prolonged heating the material becomes unduly brittle.

There is accordingly a need for hot-workable, machinable alloys and alloy articles having great strength and stability at highly elevated temperatures, and it is the principal object; of this inventionv to satisfy thisneedh This object is achieved by the present invention which comprises a heat resistant alloy containin chromium, nickel, cobalt, tungsten, and at least one metal from the group consisting of columbium, tantalum, titanium, and vanadium, together with minor quantitiesof manganese, silicon, molybdenum, carbon, nitrogen and impurities commonly present in steels of good quality.

Specifically, the alloy of the present invention contains by weight 15% to 25% chromium;- more than 25% but not more than 45% nickel;,,110'% to 25% cobalt; more than 7.5%, preferablymore than but not more than tungsten, an aggregate of 0.5% to 3 %.:0f one: 0r ,.more-ofi the elements columbium, tantalum, titanium,v and vanadium; and upto 2% manganese, up to; 1% silicon, up to 0.35% carbon, 0.05% to 025% nitrogen; and the remainder substantially alliron and incidental impurities. Up to about-3.5% molybdenum may be present, but additional molybdenum imparts no substantial benefit. The

content of an single element of the columbium,

tantalum, titanium, vanadium group should be less than 2%, and the titanium content should not exceed 1.5%. Somewhat more of the minor constituents than the upper limits just specified may on occasion be used. For instance, if excel- 2. lent forgeability is not essential; the carbon content. may be above 0.35%, up to say 1%. Iron' is present in a substantial proportion, the iron content being at least 5%.

Alloys within the foregoing composition-ranges are readily forged, welded, and machined and; as hasbeen' demonstrated by test,have remarkably great strength and stability at high temperatures, for? example 1200 F. and upwards. Machine-parts of the alloys may be designed to operate at high stressfor-long periods of time at "1500?F. and at lower stress for moderate periods atsomewhat higher temperatures. The invention" includes cast or hot-worked articles and welded articles for use-at elevated temperatures and composed of such alloys.

useful test for determining the suitabilityof metals and alloys for high temperature applications is the so-called' stress-rupture test. In this'testeach' of several'samplesof a given material is subjected to a measuredtensile stress at a particular-elevated temperature, and the time required for the sample" to fail under-these conditions of temperatureand stress is noted. The data obtained are then plotted, using time and stress as abscissa and ordinate respectively. A curve is thus established for the material tested, showing for-the selectedtemperature the time required to cause failure ofthe material when a particular stress is applied. Usually curves are established for several different temperatures,

and from these curves can be predicted quite accurately the length of time the material can withstand failure at agiven stress applied at a given temperature. This information is valuable for design purposes, especially: if I the material selected" may be 'subjectedto overheating, overloading, or both. v

The alloy article of the invention has been shown-bystress rupture tests to have excellent strength at-high temperatures and the ability to withstand large stresses for prolonged periods of time at high temperatures. 'For- 'example, in one test a specimen: of' an alloy article containing about 20%:-chromium-.;..4o% nickel, 20% cobalt;

molybdenum; 11 tungsten; 1% columbium;

'0;ll %-carbon; and 0.1 0% nitrogen, remainder substantially'all' iron withstood a-stress of 20000 pounds per square inch at a temperature of 1500 F. for 232 hours before failure. This specimen had been hot forged and then heated one hour at about 2300 F. and quenched in water before testing.

The alloy article of the invention may be forged or otherwise hot-worked without difliculty machinabl'eand has good cold or hot bending and forming properties because of its high ductility.

Another important advantage of the alloy In some article of this invention is that it may be welded,

by ordinary welding methods including the various electric arc and oxyacetylene ,fusion-deposi I tion methods, submerged-melt electric methods;

and solid-phase pressure welding methods, the

to and remote from the weld zone.

To ensure the attainment of the desirable.

characteristics of the alloy article of the invention it is most important that the composition limits setforth be adhered toso that the alloying ele-- ment are present in the proper proportions. For example, nitrogen is beneficial to high temperature properties in' the range given, but too high a nitrogen content is detrimental. SimilarlyQ if the proportions of molybdenum, tungsten, columbium, tantalum, titanium, vanadium, and carbon be higher than the ranges given, the alloy article suffers in hot-workability and weld- ,abil'ity; welds made in such alloys lack toughness and ductility. The deleterious efiects of too high proportions of these elements can not satisfactorily be cffset by increasing the proportions of cobalt and nickel in the alloy. Accordingly, care should be taken that the composition limits describedbe-observed-in making the alloy article.

If the alloy article is intended for uses in which it will be exposed to temperatures not in excess .ofabout 1350 F. compositions near the lower limits of the ranges given may be used, but if the alloy article will be used where exposure to tem .peraturesabove 1350 F. isprobable, compositions near the ,upper-limits of the-ranges given should be employed. If the alloy article is to be workable alloy consisting of to 25% chromium; more than 25% but not more than 45% nickel; 10% to 25% cobalt; more than 10% but not more than 15% tungsten; up to about 3.5% molybdenum; an aggregate of 0.5% to 3% of one or more of the elements of the group consisting of columbium,"tantalum, titanium and vanadium, the amount of any single element of the lastnamed group being less than 2% of the alloy except the titanium content being not in excess of 1.5%; up to 2% manganese; up to 1% silicon; upto 1%. carbon; 0.05% to 0.25% nitrogen; and the remainder iron and incidental impurities,

15 the iron'content being at least 5%. welds produced being sound, tough, and ductile both in the weld zone itself and in areas adjacent 2. A heat resistant alloy article which in normal use isexposed to elevated temperatures of 1200 F. and upwards and has great strength "when subjected to high stresses at such elevated used Where temperatures not in excess of 1200 F.

will be encountered, it may beused'in the cold hot-worked condition, but where exposure to temperatures above 1200 F. is expected, the the alloy article should be annealed at a tern the hot Working properties of the alloy of the in vention and the use of the alloy for wrought articles, castings of the alloy also possess very useful'properties at high temperatures.

Weclaim: l. A heat/resistant alloy article which in normal'use is exposed to elevated temperatures up- Wards of 1200 F. and has great strength and stability when subjected to high stresses at such elevated temperatures, said article being composed of a machinable, castable, weld-able, hot- Such articles may be ,perature of about 2200 F. to 2320 F. before use temperatures, said article being composed of a machinable, weldable, castable and hot-workable alloyconsisting of 15% to chromium; more than 25% but not more than 45% nickel; 10% to 25% cobalt; more than 10% but not more than 15%,tungsten; up to 3.5 molybdenum; 0.5% to less than 2% columbium; up to 2% manganese; upto 1% silicon; up to 0.35% carbon; 0.05% to 0.25% nitrogen; and the remainder iron and incidental impurities, the iron content being at least 5%.

3. A heatresistant alloy article which in normal-use is'exposed to elevated temperatures of 1200 F. and upwards and has great strength when'subjected for prolonged periods of time to high-stressesat such elevated temperatures, said article being composed of a machinable, weldable, castable and hot-workable alloy consisting substantially of,20% chromium; 40% nickel; 20% cobalt; 3% molybdenum; 11%tungsten; 1% columbium; 0.14% carbon; 01% nitrogen, the remainder iron. i e

' RUSSELL FRANKS.

WILLIAM O. BINDER.

V REFERENCES CITED, The following references are of record in the file of this patent:

UNITED STATES PATENTS published by McGraw-I-lill Book Co., N. Y., vol. II, 1940,'pages 87, 88,180, 192-194, 455.

Progress Report on NDRC Research Project, NRC-8, P. B. 39, 578, October 7, 1942, pages 1-21 inclusive"(particularly page 5); Declassified to open J anuary 28, 1946. 

1. A HEAT RESISTANT ALLOY ARTICLE WHICH IN NORMAL USE IS EXPOSED TO ELEVATED TEMPERATURES UPWARDS OF 1200*F. AND HAS GREAT STRENGTH AND STABILITY WHEN SUBJECTED TO HIGH STRESSES AT SUCH ELEVATED TEMPERATURES, SAID ARTICLE BEING COMPOSED OF A MACHINABLE, CASTABLE, WELDABLE, HOTWORKABLE ALLOY CONSISTING OF 15% TO 25% CHROMIUM; MORE THAN 25% BUT NOT MORE THAN 45% NICKEL; 10% TO 25% COBALT; MORE THAN 10% BUT NOT MORE THAN 15% TUNGSTEN; UP TO ABOUT 3.5% MOLYBDENUM; AN AGGREGATE OF 0.5% TO 3% OF ONE OR MORE OF THE ELEMENTS OF THE GROUP CONSISTING OF COLUMBIUM, TANTALUM, TITANIUM AND VANADIUM, THE AMOUNT OF ANY SINGLE ELEMENT OF THE LASTNAMED GROUP BEING LESS THAN 2% OF THE ALLOY EXCEPT THE TITANIUM CONTENT BEING NOT IN EXCESS OF 1.5%; UP TO 2% MANGANESE; UP TO 1% SILICON; UP TO 1% CARBON; 0.05% TO 0.25% NITROGEN; AND THE REMAINDER IRON AND INCIDENTAL IMPURITIES, THE IRON CONTENT BEING AT LEAST 5%. 